With increasing integration of integrated circuits, electronic devices such as power adapters and power supply apparatuses are developed toward minimization. As the volume of the electronic device is decreased, the problem associated with heat dissipation becomes more serious. Take a power adapter for example. When the power adapter operates, the electronic components mounted on the printed circuit board thereof may generate energy in the form of heat, which is readily accumulated within the closed space and usually difficult to dissipate away. If the power adapter fails to transfer enough heat to ambient air, the elevated operating temperature may result in damage of the electronic components, a breakdown of the whole power adapter or reduced power conversion efficiency. In addition, when an electronic device is in the vicinity of an electromagnetic field in the radio frequency (RF) spectrum that is caused by another electronic component, EMI (electromagnetic interference) results in operational disruption of the electronic component. Problems with EMI and heat dissipation can be minimized by placing a metallic assembly such as an EMI shielding element or a heat sink on a surface of the circuit board.
In order to attach and/or fix the metallic assembly onto the circuit board, the metallic assembly usually includes an extension plate inserting into corresponding insertion holes of the circuit board. After the extension plate is welded onto the circuit board by using a soldering material, the extension plate is fixed on the circuit board. Alternatively, the extension plate may be directly welded onto the circuit board. The metallic assembly is usually made of high thermally conductive material such as aluminum. As known, aluminum is not well bonded to the soldering material.
In order to enhance fixing effect, a conventional fixing auxiliary device for facilitating a user to fix a metallic assembly onto a circuit board is illustrated with reference to FIG. 1. The metallic assembly 12 comprises an extension plate 120 with a perforation 121. The circuit board 11 has therein an insertion hole 110. The fixing auxiliary device 13 comprises a main body 130, a screw 131 and a nut 132. The main body 130 comprises another perforation 133 corresponding to the perforation 121 of the extension plate 120. For fixing the metallic assembly 12, the main body 130 is first combined with the metallic assembly 12 when the screw 131 penetrates through the perforations 133 and 121 and is screwed into the nut 132, and then the bottom of the main body 130 is insert into the insertion hole 110. Afterward, the main body 130 is welded onto the circuit board by using a soldering material.
Since the fixing auxiliary device 13 comprises many components and the process for fixing the metallic assembly 12 onto the circuit board 11 is complicated, the use of the fixing auxiliary device 13 is not feasible. In addition, if the screw 131 is not tightly screwed into the nut 132, the metallic assembly 12 would be pivotal about the fixing auxiliary device 13 and thus the metallic assembly is not securely attached onto the circuit board 11.
In views of the above-described disadvantages, the applicant keeps on carving unflaggingly to develop an improved fixing auxiliary device according to the present invention through wholehearted experience and research.